The present invention relates generally to a microfluidic device, and more particularly, but not by way of limitation, to a microfluidic device including a microfluidic channel that is dynamically and reversibly changeable during the microfluidic chip operation.
Conventionally, devices that manipulate fluids in the microscale and nanoscale offer benefits to be used as miniaturized laboratories such as low energy consumption, shorter chemical reaction time, small sample and biological reagents consumption, low cost, high compactness, high integration and the possibility of multiple tests per device. Also, microfluidic-based devices may facilitate remote and touch-less manipulation of single cells, micro-organisms or micro-particles. Common materials used as microfludic chip substrate are silicon, glass or thermoplastic polymers such as polydimethylsiloxane (PDMS) or polymethyl methacrylate (PMMA). Standard semiconductor fabrication technology (photolithography, dry and wet etching, chemical vapor deposition, etc.) is commonly employed to manufacture microfluidic chips on silicon or glass, while methods such as injection molding or hot embossing are employed with thermoplastics.
One common aspect of these fabrication methods is that, once a microfluidic device is built, its characteristics are usually fixed and can no longer be changed. The microchannel layout, dimensions and other channel features such as the presence or absence of obstacles, pillars or surface grooves cannot be modified during chip utilization. That is, once built, the microfluidic device is generally limited to be used on the application for which it was originally designed.
One example where this results in a limitation is for microfluidic structures known as “capillary pumps”, usually comprised of a widening structure within the microchannel filled with an array of pillars that is capable of pulling fluid along the channel by means of capillary pressure. In such structures, the flow rate and volume of fluid this structure can remove depends strongly on its geometry, width, size and placement of the pillars, which are fixed by design and cannot be changed once built.
Some microfluidic devices, on the other hand, have considered using a thermorheological solution that forms a gel on heating such that, by selectively using dynamic photomasking, it results in locally gelled regions that act as channel walls. However, these devices require a liquid solution flowing or contained within a microfluidic chamber, which are hard to control in their liquid states and prone to mix with the fluid intended for analysis, and require expensive optical equipment and a photomask to be designed and built every time a change is intended for the microchannels.